Controllable wheel suspension system for an active running gear of a motor vehicle

ABSTRACT

A regulatable suspension system for an active chassis of a motor vehicle has at least two actuators which are capable of being set via actuating signals in order to influence the relative movement between a wheel of the motor vehicle and the vehicle body. A control unit is provided for generating the actuating signals as a function of input signals representing vehicle state variables. Actuating movements that can be applied to the wheel by the actuators and acting on the wheel have parallel direction components. In the event of a fault, if one actuator is defective, actuating signals coupling the actuators can be generated in such a way that a control function assigned to the defective actuator can be set via an intact actuator.

BACKGROUND AND SUMMARY OF THE INVENTION

This application claims the priority of PCT International ApplicationNo. PCT/EP99/09237, filed Nov. 27, 1999 and German patent document 19857 394.4, filed Dec. 12, 1998, the disclosures of which is expresslyincorporated by reference herein.

The invention relates to a regulatable suspension system for an activechassis of a motor vehicle.

German patent document DE 44 38 929 C1 discloses a hydraulic steeringactuator for a parameter-dependently controlled vehicle steeringarrangement, comprising a steering lever which is arranged on asteerable wheel and which is connected to the piston rod of a hydraulicsteering actuator. The steering actuator is set by means of actuatingsignals which are generated in a computer as a function of variousparameters, for example the rotary position of the steering wheel, thetraveling speed or the yaw velocity of the vehicle. The steeringactuator can be set in a regulated manner as a result of adesired-value/actual-value comparison between measured and calculatedstate variables.

Furthermore, various kinds of suspension systems for motor vehicles areknown, which comprise a plurality of components, such as spring, damperand links, and which make it possible to influence the possiblemovements of the wheel, in particular steering angle, stroke, camber andtoe in an active or passive manner as intended.

For safety reasons, the greatest possible functioning capacity of thecomponents determining the steering must be ensured. Particularly in thecase of drive-by-wire systems, in which there is no direct mechanicaltransfer of the driver's steering movement to the steered wheels, anoperating failure in the steering transmission path must be remediableby means of a usually redundant design. This results, however, inincreased production, assembly and operating costs of the suspensionsystems; moreover, redundantly designed suspension systems require moreconstruction space.

One object of the invention is to provide a regulatable suspensionsystem for an active chassis, which ensures a high degree of safety andflexibility in a simple manner.

This and other objects and advantages are achieved by the suspensionsystem according to the invention, in which redundancy is achieved byproviding at least two actuators that act upon the wheel and generateactuating movements or actuating vectors which have parallel directioncomponents. This is achieved by providing an angle other than 90°between the actuating directions of the two actuators, so that theeffective directions of the two actuators are at least partiallysuperposed on one another. Thus, when there is a fault due to a defectof one actuator, the function of the latter can be at least partiallyperformed by the second actuator.

The operating state of the actuators is checked regularly via a controlunit and, when a failure of one actuator is detected, actuating signalsacting upon the remaining (intact) actuator are generated. Theseactuating signals cause the intact actuator to perform the function ofthe defective actuator, by intensifying the actuating movement of theintact actuator or to adapting it in the effective direction of thedefective actuator until the function of the defective actuator isperformed completely or partially.

This novel concept achieves a reduction of the number of components inthe suspension system, because it is no longer necessary to provide areplacement actuating element for each actuator in order to ensure thenecessary operating reliability. Instead, it is possible to achieveredundancy for a plurality of actuators using only a single additionalactuator which performs additional functions that correspond to theprimary functions of the other actuators. Furthermore, a graded safetystrategy can be implemented, in which only those actuators that areparticularly relevant to safety are protected redundantly.

In one embodiment of the invention, the actuating direction of theadditional actuator has a direction component which runs parallel to theactuating direction of at least two further actuators. In the event of afault, the additional actuator can perform the function of the defectiveactuator, so that it is possible to ensure a safeguard against theoperating failure of at least two actuators, by means of only oneadditional actuator.

In another expedient version, in the event of a fault an actuator whichsets a less safety-relevant function of the suspension system alsoperforms the function of a defective actuator that is more important insafety terms. And if appropriate, it can also be taken into account thatthe intact actuator can no longer (or no longer completely) perform itsoriginal function. For example, it is possible to cause a defectivesteering function of one actuator to be performed by a further actuatorwhich is responsible primarily for setting the camber or the toe of thewheel. The actuator performing the steering function generates anactuating movement with a direction component which is parallel to theactuating direction of the defective actuator responsible primarily forsteering. By means of the control, the intact actuator can be activatedso that the direction component influencing the steering is aspronounced, or at least approximately as pronounced, as the actuatingmovement of the steering actuator. Thus, the steering function cancontinue to be exercised without any safety restriction.

When the function of a defective actuator is assumed by an actuator thatis used primarily for another function, the number of all the actuatorsused corresponds to the number of influenceable possibilities for themovement of the wheel. No additional actuators are required in thisversion, yet a redundant design is achieved due to function assumption.

It may be expedient, if appropriate, to design two or more actuatorssuch that, in the event of a fault, mutual function assumption ispossible. In this general case, when all the actuators are fullyoperational, the actuating movements of the actuators are normallyuncoupled, so that each actuator performs only the primary functionassigned to it. In the event of a fault, if there is a partial orcomplete failure of one or more actuators, the functions of the intactactuators are coupled, while their main functions either continue to beperformed at least approximately or are relinquished in favor of themore important functions of the defective actuators. The uncoupling andcoupling of the actuators is carried out with the aid of the actuatingsignals which are generated in the control.

In a preferred embodiment, the force application points of twocooperating actuators are arranged in each case at a distance from thesteering axis, so that both actuators can influence the steering angle.If one of the actuators fails, the remaining actuator can be used forsteering.

Advantageously, the force application points of the two actuators arealso at a distance from a further wheel rotation axis, so that both cangenerate a torque acting about this wheel rotation axis, in order to seta further degree of freedom of the wheel; in particular camber or toe.If one actuator fails, the remaining operational actuator can assume thesteering function, if appropriate with the function for setting theadditional degree of freedom of the wheel being reset.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a wheel module with a plurality ofactuators;

FIGS. 2 to 12 to show further exemplary embodiments of wheel moduleswith different numbers of actuators or different actuator arrangements.

DETAILED DESCRIPTION OF THE DRAWINGS

In the exemplary embodiments illustrated in FIGS. 1 to 12, identicalcomponents are given the same reference symbols. Wheel rotation ispresumed hereafter to be self-evident and is not included as anindependent degree of freedom. Vertical compression usually also resultsin a damping of the vertical movement of the wheel. In all the exemplaryembodiments, there is a control unit for generating actuating signalsacting upon the actuators.

The wheel module or suspension system 1, shown in FIG. 1, for a wheel 2is part of an active regulatable chassis in a motor vehicle. Thesuspension system comprises a plurality of actuators 3 to 8 which arecombined into a spatial system and act upon the wheel 2 or the wheelcarrier of the wheel 2. The actuators 3 to 8, which are designed astranslationally acting piston/cylinder adjustment devices, are set to adesired position, via actuating signals S_(St) generated in a controlunit 9 according to predetermined control instructions, as a function ofinput signals S_(E). The latter are recorded, for example, bymeasurement transducers and represent state variables and operatingvariables of the motor vehicle.

The six actuators 3 to 8 form a spatial hexapod and make it possible toimplement a total of six degrees of freedom of the wheel: steering,compression, camber setting, toe setting and wheel-base change (bothlongitudinally and transversely). Each of the actuators is connected tothe vehicle body at its end remote from the wheel carrier, with pairs ofactuators (3-4, 5-6 and 7-8) being fastened at common fastening point10, 11, 12. Each common fastening point 10, 11 or 12 combines with twoof the opposite force application points (13-15, 13-14 and 14-15) of theassociated actuators to form a triangle (10-13-15, 11-14-13 and12-15-14). Adjacent pairs of actuators (3-5, 6-8 and 4-7) share a commonforce application point 13, 14, 15 with the actuating direction ofadjacent actuators at a common force application point differingaccording to the angle formed between two actuators.

In each case two actuators suspended at a common fastening point lie ina common plane; the actuators suspended at different fastening pointslie in different planes. The plane of the actuators 5, 6 runs at aslight inclination to the vertical. The force application points 13, 14of the actuators 5, 6 lie, directly adjacent to the wheel 2, in anapproximately horizontal line; the force application points 13, 14 areat a lateral distance from the wheel axle 16 and at a vertical distancefrom the wheel contact point 23.

The force application point 15 of the actuators 4 and 7 is located at ahorizontal distance from the wheel body on the wheel axle 16. The threeforce application points 13, 14, 15 form the triangle, depicted byhatching, which runs approximately horizontally slightly above the wheelaxle 16. The three planes, which are formed in each case by twoactuators suspended at a common fastening point, limit three sides of atetrahedron.

The degrees of freedom which can be executed by means of thisconfiguration are: steering, compression, camber setting, toe increaseand wheel-base change. All six of these functions can be exercisedsimultaneously when all six actuators 3 to 8 are operational. With theaid of the actuating signals S_(St) generated in the control unit 9, thefunctioning of the individual actuators is coordinated in such a waythat, in spite of the common force application points, uncoupling of thedegrees of freedom is achieved during normal operation when theactuators are fully operational, so that the degrees of freedom can beactivated without influencing one another.

In the case of a defective actuator, such actuator is detained in itscurrent position or in a convenient position in terms of energy, forinstance in its central position, which position is even kept under theinfluence of external forces. The defective actuator then assumes thefunction of a fixed transmission rod. The defective actuator may bedetained, for example, by means of an electric motor having aself-locking worm gear.

It may also be expedient, however, to refrain from any detention of adefective actuator and to cause it to slide under the influence ofexternal forces.

In the event of a fault, even if there is a failure of one or moreactuators, the steering, compression and camber-setting functions canstill be performed. Since each actuator has an actuating direction withforce components perpendicular to the steering plane containing thesteering axis, it is possible, even if five actuators fail, to carry outwheel steering by means of any one intact actuator only. By virtue ofthe spatial arrangement in which each actuator assumes in relation tothe wheel 2 an actuating direction deviating from that of the adjacentactuators, and has a direction component parallel to each adjacentactuator, it is possible to implement the steering, compression andcamber-setting functions by means of any three intact actuators only,the remaining degrees of freedom being relinquished. As a result,overall, a considerable safety reserve is obtained. Moreover, thereremains, as a rule, at least a diminished capacity to influence theother relinquished degrees of freedom.

FIG. 2 illustrates a further exemplary embodiment of a suspension system1 for a wheel 2 with altogether four actuators 3 to 6, by means of whichthe four degrees of freedom comprising steering, compression, cambersetting and toe setting can be influenced; in the figure, the movementarrows 17, 18 and 19 illustrate the possible steering, compression andcamber-setting movements of the wheel 2.

The four actuators 3 to 6 are arranged spatially in the same way as inthe preceding embodiment. In each case two actuators 3, 5 and 4, 6terminate at a common wheel-side force application point 13 and 15, thetwo force application points 13, 15 at the same time forming, togetherwith a further point of articulation 21, corner points of a steeringtriangle 20 which is arranged on the wheel side and which transmits theactuating movements of the actuators 3 to 6 to the wheel 2. The steeringtriangle 20 runs approximately vertically and lies approximatelyparallel to the wheel rotation plane. The two force application points13 and 15 are located at a lateral distance from the steering axis 24and at a vertical distance from the wheel contact point 23.

The two actuators 3 and 4 with the lower force application points 13 and15 have a common body-side fastening point 10, run approximatelyhorizontally and form a common angle.

The two actuators 5 and 6 lie approximately parallel to one another;they are suspended on the body side, via two fastening points 11, 12, toa further approximately horizontal steering triangle 22, the thirdcorner point of which is identical to the point of articulation 21 ofthe first steering triangle 20. The fastening points 11, 12 are locatedabove the fastening points 10 of the actuators 3 and 4. The actuators 5and 6 lie obliquely in the suspension system 1, and the actuatingdirections of the actuators 5 and 6 are identical to one another, butdiffer from the actuating directions of the other two actuators 3, 4.Since the actuating direction of the actuators 5, 6 forms with theactuating direction of the actuators 3, 4 an angle other than 90°, adirectional component of the actuating direction of each actuator 5, 6coincides with a direction component of the actuating direction both ofthe actuator 3 and of the actuator 4.

In the event of a failure of an actuator, detected by a control unit(not shown), the faulty actuator is deactivated, so that the piston canslide freely in the cylinder of the actuator. As long as at least oneactuator is still intact, at least the steering function can continue tobe performed in the event of a fault.

FIGS. 3, 3 a and 3 b illustrate a further exemplary embodiment. FIG. 3is a perspective view, while FIG. 3a is a side view and FIG. 3b a topview of the exemplary embodiment. The suspension system 1 of the wheel 2comprises a total of four actuators 3 to 6 which are suspended on thebody at four different fastening points 10, 11, 12, 28 and are connectedto a wheel-side link 25 via four different force application points 13,14, 15, 26. Both the force application points and the fastening pointsof the actuators in each case form a rectangle. In each case twomutually spaced actuators 3-5 and 4-6 lie parallel to one another;actuators 3-4 and 5-6, with fastening points and force applicationpoints located approximately vertically one above the other, are at anangle to one another. A steering triangle 20 is also provided, whichruns approximately horizontally and is connected to the wheel axle 16and to the link 25 via a point of articulation 27.

The suspension system possesses a total of the three degrees of freedomcomprising steering, compression and camber setting. Since the number ofactuators exceeds the number of degrees of freedom, the system has aredundant design. Normally, on account of the redundant design, thesurplus actuator can be used for force regulation, in order to preventdistortions which may be caused by actuators running asynchronously.

If only one actuator fails, the defective actuator is put into a slidingposition, and all the degrees of freedom can be executed withoutadversely affecting one another. If two actuators fail, the steerabilityof the system can be preserved, but with the compression andcamber-setting functions being coupled.

The suspension system 1 according to FIG. 4 comprises two approximatelyhorizontal actuators 3 and 4 which run approximately parallel and areconnected via the force application points 13, 14 to an approximatelyvertical wheel-side steering triangle 20 fastened to a further steeringtriangle 22. The system possesses two degrees of freedom: the wheel 2can be steered about its steering axis 24 according to the movementarrow 17 and the wheel camber can be set according to the movement arrow19. If one actuator fails, steerability can be maintained.

The exemplary embodiment having the suspension system according to FIG.5 corresponds in its make-up to that according to FIG. 4, but has anadditional actuator 5 which, as an additional degree of freedom, allowsthe compression of the wheel 2. Moreover, there is the possibility ofalso adjusting the toe of the wheel in addition to steering, cambersetting and compression. On account of the coupling of steering andcamber setting or of camber setting and toe setting, the number ofdegrees of freedom amounts to three. There is no risk of distortion ofthe suspension system 1 as a result of actuators running asynchronously.The version according to FIG. 5, like the version according to FIG. 4,may also be used as an axle module by transferring the arrangement in amirror image onto the other side of the vehicle, in which case commonhorizontal actuators can be used, so that identical steering and camberangles can be set on both steerable vehicle wheels.

If one actuator fails, it is put into a detained position. Steerabilityis not adversely affected by the failure of one actuator, but at allevents there is coupling between steering and camber setting.

FIG. 5a shows schematically the associated movement space of the wheel2. When the actuators 3 and 4 are simultaneously elongated in the samedirection, the wheel 2 is cambered. In the event of elongation in theopposite direction, the toe of the wheel is set or steering is carriedout.

FIGS. 6, 6 a and 6 b illustrate a modified version of the example fromFIG. 5. FIG. 6 is a perspective view, while FIG. 6a a top view and FIG.6b a side view, but with offset actuators. The suspension system 1 forthe wheel 2 comprises two horizontal actuators 3, 4, which engage on awheel-side transverse link 30, and a vertical actuator 5 on the steeringaxis 24. The steering axis 24 is connected to the wheel axle 16. Thelower end of the steering axis 24 is connected to a steering triangle 22which is suspended on the body; the upper end of the steering axis 24 isguided movably in a transverse guide 29, in the form of a part circle,which is fastened to the body.

The system possesses the three degrees of freedom comprising steering,compression and camber setting according to the movement arrows 17, 18and 19. Toe setting is coupled to camber setting. The transverse guide29 ensures an exact movement of the steering axis 24 during the settingof the camber.

As a comparison of FIGS. 6 and 6b shows, the horizontal actuators 3, 4arranged in parallel may be arranged both above and below the transverselink 30.

FIG. 7 shows a device similar to that of FIG. 6, but with the differencethat the transverse guide 29 can be detained by means of an auxiliaryactuator 31, so that the camber movement of the steering axis 24 isblocked.

In the event of a fault, the defective actuator is put into a slidingposition, in contrast to the preceding exemplary embodiment. At the sametime, the auxiliary actuator is activated and camber movement of thesteering axis is prevented. The steering function can be performedwithout restriction.

FIG. 8 shows a mirror-symmetrical arrangement of the version accordingto FIG. 4, with two common actuators 3, 4 for two steered wheels of anaxle. On account of the actuators 3, 4 used jointly for both wheels, theentire system with both wheels has only the two degrees of freedomcomprising steering and camber setting; these degrees of freedom areexecuted in the same way for both wheels.

The example shown in FIG. 9 shows the implementation of a steeringfunction with single redundancy. Two actuators 3, 4 running essentiallyhorizontally are provided, which are suspended on the body side and actupon the steering triangle 20. A further actuator 5 running obliquely isconnected to the horizontal actuator 3 at a distance from the body-sidefastening of the latter. The system can be steered and can be compressedand the camber can be set, with the camber setting being capable ofbeing carried out independently of the steering. Steering may, ifappropriate, be carried out via a single one of the three actuators. Itis possible to set the camber only by actuating the two horizontalactuators 3 and 4 simultaneously and in the same direction.

In the event of a defect of either actuator 3, 4, the faulty actuator isput into the detained position. Although the wheel 2 can continue to besteered, camber setting is no longer possible.

FIG. 10 shows a wheel module with two essentially parallel actuators 3,4 running obliquely. The actuators 3, 4 act upon a transverse link 30which is mounted above the wheel axle 16 and which is connected to anupper horizontal steering triangle 22 and, via a passive spring damperelement 33, to a lower steering triangle 32. The spring damper element33 is mounted on the wheel axle 16. The system possesses three degreesof freedom: steering, compression and chamber. The steering andcompression movements are coupled, so that a steering movement isconverted, as a function of the compression, into a correspondingactuating movement for producing a wheel steering angle, and alsoindependent camber setting.

In the event of a fault, the defective actuator is put into a slidingposition. The steering function can continue to be carried out, but as afunction of the compression. Distortion of the wheel suspension as aresult of actuators running asynchronously is not to be expected.

As a result of the upwards or downwards displacement of the uppersteering triangle 22 in the direction of the movement arrow 34, cambersetting can likewise be brought about.

FIGS. 11a and 11 b illustrate a further exemplary embodiment. Thesteering angle is set via a steering actuator 3 which acts on the wheelaxle 16 via a transverse link 30. A passive spring damper element 33 issupported on a shock-absorbing strut 35 which is clamped between abody-side support and a lower steering triangle 32. The spring damperelement 33 makes it possible to have a vertical compression of the wheel2 of the suspension system 1 as a further degree of freedom.Furthermore, the upper end of the shock-absorbing strut 35 has arrangedon it an actuator 5 which can normally be both detained and activated.With the actuator 5 activated, the compression function is performed viathe actuator 5 which is additionally used for the passive spring damperelement 33.

In the event of a fault, if the steering actuator 3 fails, the latter isadjusted into the sliding position and the vertical actuator 5 isactivated. At the same time, an auxiliary actuator 31 is moved up to theshock-absorbing strut 35 and is brought into engagement with an externalthread on the shock-absorbing strut 35, so that an up-and-down movementof the shock-absorbing strut 35 caused by the actuator 5 in thedirection of the movement arrow 18 automatically brings about a rotationof the shock-absorbing strut 35. This rotational movement can beconverted in a controlled way into a steering movement according tomovement arrow 17, but at the expense of active suspension which in thiscase is assumed solely by the passive spring damper element.

The exemplary embodiment according to FIG. 12 constitutes an extendedcombination of the examples from FIG. 7 and FIGS. 11a and b. Twoparallel horizontal actuators 3, 4 are provided, which act upon atransverse link 30 connected via the steering axis 24 to the wheel axle16. The vertical shock-absorbing strut 35 is provided with a passivespring damper element 33 and with an actuator 5. Furthermore, anactuator 6 in the transverse guide 29 and two auxiliary actuators 31 and31′ are provided. The first auxiliary actuator 31 can be pushedlaterally up to the shock-absorbing strut 35 and, in the bearingposition, engages by meshing into an external thread on theshock-absorbing strut 35. In the bearing position, the second auxiliaryactuator 31′ engages into the transverse guide 29 at the upper end ofthe shock-absorbing strut 35, whereupon a camber movement in thedirection of the movement arrow 19 is blocked. A camber movement can begenerated actively as a result of the actuation of the actuator 6 in thetransverse guide 29.

Normally, steering can be carried out and the camber can be set via theparallel actuators 3 and 4. Compression can be influenced via thevertical actuator 5. The actuator 6 is either put into the slidingposition or synchronized with the camber setting of the parallelactuators 3 and 4.

If one of the two parallel actuators 3 and 4 fails, in a first variantthe auxiliary actuator 31′, designed as a detent pawl, can snap into amiddle position in the transverse guide 29, whereupon steering can becarried out by means of the intact second parallel actuator. Thedefective actuator is put into the sliding position.

In a second variant, steering and camber setting are coupled, by thedefective actuator being put into the detaining position and the drivetaking place either via the intact parallel actuator or via the actuator6 arranged in the transverse guide. In this variant, steering and camberadjustment are coupled.

Should both horizontal parallel actuators 3 and 4 fail, the auxiliaryactuator 31 is moved, in a bearing position, onto the external thread ofthe shock-absorbing strut 35 and the auxiliary actuator 31′ isintroduced, in the blocking position, into the transverse guide 29. Avertical movement executed by the actuator 5 is converted into asteering movement as a result of the meshing engagement of the auxiliaryactuator 31 into the external thread on the shock-absorbing strut 35.

A steering with triple redundancy is achieved by the use of theadditional auxiliary actuators 31 and 31′.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed is:
 1. A regulatable suspension system for an activechassis of a motor vehicle, comprising: at least two actuators forcontrolling relative movement between a wheel of the motor vehicle and avehicle body; and a control unit for generating actuating signals forsetting actuating movements of said actuators as a function of inputsignals representing vehicle state variables; wherein actuatingmovements which can be generated by the at least two actuators, actingon the wheel, have parallel direction components; and in the event of afailure of one actuator, actuating signals coupling the actuators can begenerated to control a degree of freedom previously controlled by thefailed actuator, via an intact actuator.
 2. The suspension systemaccording to claim 1, wherein pairs of the at least two actuators lie ina common plane.
 3. The suspension system according to claim 2, wherein apair of actuators lying in a common plane are arranged at an angle toone another and have a common intersection point.
 4. The suspensionsystem according to claim 2, wherein a pair of actuators lie parallel toone another.
 5. The suspension system according to claim 1, wherein twoforce application points of the at least two actuators, and a furtherpoint of articulation, are arranged at respective corner points todefine a triangle.
 6. The suspension system according to claim 1,wherein, in the event of failure of an actuator, a function of thefailed actuator is assumed by an intact actuator, in addition to aprimary function assigned to the intact actuator.
 7. The suspensionsystem according to claim 1, wherein in the event of a failure of anactuator a primary function of an intact actuator can be eliminated,with the intact actuator assuming a function of the defective actuator.8. The suspension system according to claim 1, wherein force applicationpoints of two cooperating actuators for applying actuating force to thewheel are offset from the steering axis.
 9. The suspension systemaccording to claim 8, wherein the force application points of the twocooperating actuators are also offset from a wheel rotation axis. 10.The suspension system according to claim 8, wherein in the event of afailure of an actuator, said control unit operates actuating signalswhich set a steering angle for the vehicle via a remaining intactactuator.
 11. The suspension system according to claim 8, wherein avehicle steering angle and camber of a wheel can be manipulated via thetwo cooperating actuators.
 12. The suspension system according to claim8, wherein a vehicle steering angle and toe of a wheel can bemanipulated via the two cooperating actuators.
 13. The suspension systemaccording to claim 8, wherein a vehicle steering angle and a stroke ofthe body in relation to a wheel (2) can be manipulated via the twocooperating actuators.
 14. The suspension system according to claim 1,wherein in the event of a failure of an actuator, a failed actuator canbe detained.
 15. The suspension system according to claim 1, wherein inthe event of a failure of an actuator, a failed actuator is held in asliding position.
 16. The suspension system according to claim 1,wherein more than two actuators are provided, a force vector of eachactuator having a force component which is parallel to a force componentof at least one of the other actuators.
 17. The suspension systemaccording to claim 1, wherein the actuators comprise hydrauliccylinders.
 18. A vehicle suspension apparatus, comprising: a vehiclewheel; a plurality of actuators coupling respective force applicationpoints associated with the wheel to fastening points on a vehicle body;and a control unit for generating actuating signals for actuatingmovement of said actuators to control a plurality of degrees of freedomin movement of said wheel; wherein each of said actuators is oriented inspace along a directional axis which has a directional component that isparallel to a directional axis of at least one other actuator; and uponfailure of an actuator, said control unit controls an intact actuatorhaving a directional axis parallel to a directional component of adirectional axis of the failed actuator, to perform a control movementof said wheel that was previously performed by the failed actuator. 19.A vehicle suspension apparatus according to claim 18, wherein, uponoccurrence of such a failure, said control unit controls the failedactuator such that it is one of held in a fixed position and movable.20. A vehicle suspension apparatus according to claim 18, wherein eachof said actuators can be actuated to perform a steering function forsaid vehicle wheel.